This invention relates to an improved cereal grain milling system that includes at least one disc mill and also to an improved bran removal machine suit-able for use in such a milling system.
Disc mills such as that described in Anderson U.S. Pat. No. 4,667,888 provide important advantages over conventional roller mills in terms of reduced capital, operating, and maintenance costs combined with increased ease of operation and reduced space requirements. Such disc mills have found use in commercial milling operations, particularly in regrind operations, where most of the bran layer of the grain has been removed and the disc mill operates to reduce the size of the endosperm. However, problems have been encountered that have limited the use of disc mills in the first break position. In particular, when whole grain with an intact bran layer is milled in a disc mill in the first break position, the bran layer is cut into small fragments which can prove difficult to remove efficiently. This disadvantage of disc mills has in the past limited their use.
Accordingly, it is an object of this invention to provide a milling system which allows increased usage of disc mills, and in particular to provide a milling system in which a disc mill can be used efficiently in the first break position.
Another development in milling technology relates to milling systems which combine roller mills with bran removal machines upstream of the roller mills. U.S Pat. application Ser. Nos. 07/557,631 and 07/610,819, assigned to the assignee of the present invention, disclose several such systems. Also of interest in this connection are Satake U.S. Pat. No. 4,741,913 and Tkac European patent applications 0 295 774 and 0 373 274. In all of these milling systems one or more bran removal machines are used to remove the outer bran layer from a quantity of wheat without reducing the size of the endosperm to produce a pearled wheat. This pearled wheat is then introduced into a conventional roller mill as part of a flour making operation.
U.S. Pat. applications Ser. Nos. 07/557,631 and 07/610,819 disclose the use of a vertical flow bran removal machine in which a central rotor is rotated about a vertical axis and the wheat being pearled passes in an annular column between inner and outer abrasive elements. Such a vertical bran removal machine has been found to provide high output and efficient operation. However, the amount of bran that can be efficiently removed in a single pass through a vertical bran removal machine of the type described above is limited.
It is accordingly an object of this invention to provide an improved vertical bran removal machine that is capable of removing an unusually large amount of bran in a single pass.